Fuel pump

ABSTRACT

Fuel pump ( 10 ) may comprise a housing ( 12 ), a motor ( 30 ) disposed within the housing, and a motor cover ( 16 ) attached to one end of the housing. The motor may include a motor shaft ( 32 ). The motor cover may comprise a bearing retaining portion ( 22 ) and a discharge port ( 26 ). The bearing retaining portion retains a bearing ( 28 ) that rotatably supports one end of the motor shaft. The discharge port may be formed concavely from the outer surface of the motor cover. A fuel pipe ( 50 ) is inserted into the discharge port. The bearing retaining portion may be formed in a center of the inner surface of the motor cover. The discharge port may be disposed in a position shifted from the bearing retaining portion.

CROSS REFERENCE

This application claims priority to Japanese Patent application number 2005-67677, filed on Mar. 10, 2005, the contents of which are hereby incorporated by reference as if fully set forth herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a fuel pump for drawing in a fuel such as gasoline etc., increasing the pressure thereof, and discharging the pressurized fuel.

2. Description of the Related Art

A known fuel pump generally comprises a housing, a pump casing attached to a lower end portion of the housing, and a motor cover attached to an upper end portion of the housing. An intake hole is provided in the lower surface of the pump casing. A discharge port is provided in the upper surface of the motor cover. The discharge port protrudes from the upper surface of the motor cover. A motor is accommodated inside a motor chamber defined by the housing, pump casing, and motor cover (i.e., space inside the housing). The lower end of the motor shaft is rotatably supported on the pump casing, and the upper end of the motor shaft is rotatably supported on the motor cover. An impeller is rotatably disposed within the pump casing. The impeller is connected with the lower end of the motor shaft. When the motor rotates, the impeller also rotates and a fuel is drawn into the pump casing from the intake hole. The pressure of the fuel drawn into the pump casing rises and the fuel is discharged from the discharge port through the motor chamber.

This type of fuel pump is usually disposed within the fuel tank. As a result, the length of the fuel pump in the axial direction is restricted by the shape of the fuel tank. In recent years, fuel tanks have tended to become flatter. In particular, flattened fuel tanks for automobiles are designed to enable the enlargement of space inside the automobile, without increasing the size of the automobile body. Therefore, there is need for the axial length of the fuel pump to be shorter as well.

In the conventional fuel pump, a discharge port protrudes from the upper surface of the motor cover, and the discharge port is inserted into a fuel pipe (e.g., hose, etc.). Therefore, the diameter of the discharge port is made less than the diameter of the fuel pipe. On the other hand, because the pressurized fuel flows from the discharge port into the fuel pipe, the discharge port and the fuel pipe have to be strongly joined. Thus, the surface area of the joint portion of the discharge port and the fuel pipe has to be somewhat increased to obtain a strong joint thereof. Since the diameter of the discharge port is less than the diameter of the fuel pipe, the length of the discharge port has to be increased to a certain extent in order to join strongly the discharge port and the fuel pipe. For this reason, in the conventional fuel pumps, it is difficult to shorten the discharge port. Therefore, the length of the fuel pump in the axial direction is increased by the length of the discharge port.

Japanese Laid-Open Patent Publications No. 2004-293526 and 2003-286924 disclose fuel pumps in which the discharge port is formed concavely from the upper surface of the motor cover. However, in those fuel pumps, the discharge port is disposed in the center of the motor cover (i.e., on a central axis line of the fuel pump). Because a bearing that supports the motor shaft is disposed in the center of the motor cover, the discharge port has to be disposed above the bearing. As a result, the length of such fuel pump in the axial direction is structurally also difficult to decrease.

SUMMARY OF THE INVENTION

Accordingly, it is one object of the present teachings to provide a fuel pump that makes it possible to decrease the length of the fuel pump in the axial direction, thereby improving installation ability on a fuel tank.

In one aspect of the present teachings, fuel pump may comprise a housing, a motor disposed within the housing, and a motor cover attached to one end of the housing. The motor may include a motor shaft. The motor cover may comprise a bearing retaining portion and a discharge port. The bearing retaining portion retains a bearing that rotatably supports one end of the motor shaft. The discharge port may be formed concavely from the outer surface of the motor cover. A fuel pipe is inserted into the discharge port. When the motor shaft rotates, a fuel is drawn into the housing and discharged to the fuel pipe from the discharge port. The bearing retaining portion may be formed in a center of the inner surface of the motor cover. The discharge port may be disposed in a position shifted from the bearing retaining portion.

In this fuel pump, the fuel pipe is inserted into the discharge port. Therefore, the diameter of the discharge port can be made larger than the outer diameter of the fuel pipe. Thus, the surface area of the joint portion of the fuel pipe and discharge port can be ensured even if the length of the discharge port is shorter than that of the protruding discharge port. Furthermore, because the discharge port is disposed in a position shifted from the bearing retaining portion, the bearing retaining portion and the discharge port can be disposed so as to overlap in the axial direction. As a result, the length of the fuel pump in the axial direction can be shortened and the installation ability on a fuel tank can be improved.

Preferably, a fuel channel formed in the motor cover extends linearly from the inner surface of the motor cover toward the discharge port. Because channel resistance to the fuel flow from inside the housing to the discharge port is decreased, the pump efficiency can be increased.

In another aspect of the present teachings, the motor may comprise a commutator and a brush that comes into contact with the commutator. The motor cover may comprise a brush retaining portion for retaining the brush. The brush retaining portion may be formed in the inner surface of the motor cover. Preferably, the brush retaining portion and the discharge port are arranged side by side in the circumferential direction, and the bearing retaining portion, discharge port, and brush retaining portion are arranged so as to overlap in the axial direction.

In this fuel pump, because the brush retaining portion and discharge port are arranged side by side in the circumferential direction of the fuel pump, the brush retaining portion can be arranged in a position close to the axial center of the motor shaft. As a result, the commutator diameter is reduced and the circumferential speed of the commutator is decreased, thereby making it possible to suppress the wear on the brush. Furthermore, because the bearing retaining portion and the discharge port and the brush retaining portion overlap in the axial direction, the axial length of the fuel pump can be shortened.

In the above-described fuel pumps, the wall that forms the bearing retaining portion can be shared with the wall that forms the discharge port. Alternatively, the wall that forms the discharge port can be shared with the wall that forms the brush retaining portion. Alternatively, the wall that forms the bearing retaining portion can be shared with the wall that forms the brush retaining portion. Sharing the walls that form the adjacent portions (i.e., bearing retaining portion, brush retaining portion, or discharge port) makes it possible to dispose the portions close to each other and to make the fuel pump compact in the radial direction.

In another aspect of the present teachings, the motor cover may include a fuel discharge hole which is formed in the bottom surface of the discharge port. Preferably, a return check valve for opening and closing the fuel discharge hole is installed in the discharge port, and the return check valve is positioned on the outer side of the fuel pipe in a state where the fuel pipe is inserted into the discharge port.

In this fuel pump, the fuel pipe and return check valve are disposed side by side in the axial direction of the fuel pump. Because the return check valve is not disposed inside the fuel pipe, the shape of the return check valve is not restricted by the shape of the fuel pipe and the diameter (i.e., seal diameter) of the return check valve can be increased. As a result, pressure sensitivity of the return check valve can be increased and the return check valve can be operated with good stability even when the stroke of the return check valve is small. Furthermore, because the stroke of the return check valve can be reduced, the length of the discharge port can be shortened.

When the return check valve is installed in the discharge port, it is preferred that a guide for guiding the return check valve be further provided in the discharge port. With such a configuration, the return check valve is prevented from tilting inside the discharge port and operability of the return check valve can be ensured.

These aspects and features may be utilized singularly or, in combination, in order to make improved fuel pump. In addition, other objects, features and advantages of the present teachings will be readily understood after reading the following detailed description together with the accompanying drawings and claims. Of course, the additional features and aspects disclosed herein also may be utilized singularly or, in combination with the above-described aspect and features.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically shows a fuel pump of a representative embodiment of the present teachings and a fuel filter that will be connected to the fuel pump.

FIG. 2 is a cross-sectional view perpendicular to the axial direction of the fuel pump.

FIG. 3 is a cross-sectional view along line III-III of FIG. 2.

FIG. 4 is an enlarged view of the joint section of a discharge port and a fuel pipe.

FIG. 5 shows another example of the joint section of a discharge port and a fuel pipe.

FIG. 6 shows another example of the joint section of a discharge port and a fuel pipe.

FIG. 7 shows another example of the joint section of a discharge port and a fuel pipe.

FIG. 8 shows another example of the motor cover of the present teachings (state in which the fuel pipe is not inserted).

FIG. 9 is an enlarged view of a joint portion of the discharge port shown in FIG. 8 (a state in which the fuel pipe is inserted).

FIG. 10 is a plan view of the guide (a state where the return check valve is assembled).

FIG. 11 is a plan view of the guide (a state where the return check valve is not be assembled).

FIG. 12 shows another example of the motor cover of the present teachings (state in which the fuel pipe is not inserted).

FIG. 13 shows another example of the motor cover of the present teachings (state in which the fuel pipe is not inserted).

DETAILED DESCRIPTION OF THE INVENTION

A fuel pump 10 according to a representative embodiment of the present teachings will be described below. Fuel pump 10 may be used in an automobile, fuel pump 10 being utilized within a fuel tank and being utilized for supplying fuel to an engine of the automobile. As shown in FIG. 1, fuel pump 10 comprises a housing 12, a pump casing 11 attached to the lower end of housing 12, and a motor cover 16 attached to the upper end of housing 12.

A pump chamber is formed inside pump casing 11. An impeller (not shown in the figure) is rotatably disposed within pump casing 11. A fitting hole is formed in the center of the impeller. A shaft 32 (described below) of a motor 30 fits into the fitting hole of the impeller. Thus, when motor 30 rotates, the impeller also rotates.

An intake hole (not shown in the figure) is formed in pump casing, the intake hole extending from the lower surface of the pump casing 11 to the pump chamber. The Intake hole is connected to the pump chamber and the outside of fuel pump 10. Further, a discharge passage (not shown in the figure) is formed in pump casing, the discharge passage extending from the upper surface of pump casing 11 to the pump chamber. The discharge passage is connected to the pump chamber and the inside of the housing 12.

As shown in FIGS. 2 and 3, motor 30 is accommodated inside housing 12 (more specifically, in the space defined by housing 12, pump casing 11, and motor cover 16). Motor 30 is a direct current motor comprising brushes 38, a magnet (permanent magnet) fixed to the inner surface of housing 12 and an armature 31 installed coaxially with magnet 14.

Armature 31 comprises a shaft 32, a core fixed to shaft 32, a coil wound around the core, and a commutator 34 for supplying current to coil 36. The lower end of shaft 32 is rotatably supported by the pump casing 11. The upper end of the shaft 32 is rotatably supported by the motor cover 16 via a bearing 28. Bearing 28 is mounted in a bearing retaining portion 22 formed in a center of the lower surface of motor cover 16.

Two brushes 38, 38 are brought into contact with the upper surface of commutator 34. Brushes 38, 38 are accommodated in the brush retaining portions 24, 24 formed in the lower surface of motor cover 16 (see FIG. 3). Compressed springs 18 are disposed between each brush 38 and motor cover 16. Therefore, brushes 38, 38 are constantly pressed against commutator 34 with springs 18. If brushes 38, 38 are worn, springs 18 extend accordingly and the contact state of brushes 38, 38 and commutator 34 is maintained.

Motor cover 16 is formed from resin. Motor cover 16 is a substantially disk-shaped. Motor cover 16 is attached to housing 12 by caulking the upper end 12 a of housing 12. Bearing retaining portion 22 and brush retaining portions 24 are formed in the lower surface of motor cover 16. A discharge port 26 is formed in the upper surface of motor cover 16.

Discharge port 26 is formed concavely so as to be recessed from the upper surface of motor cover 16. The axial line of discharge port 26 is substantially parallel to the axial line of fuel pump 10 (i.e., the axial line of shaft 32). As shown in FIG. 1, a fuel pipe 50 is inserted into discharge port 26. For this purpose, the shape of discharge port 26 corresponds to the outer shape of fuel pipe 50, and the diameter of discharge port 26 is substantially equal to the outer diameter of fuel pipe 50.

Furthermore, a discharge hole 25 passing through to the lower surface of motor cover 16 is formed in the bottom surface of discharge port 26. Discharge hole 25 communicates between the inner space of housing 12 and discharge port 26. Discharge hole 25 is formed in a straight vertical line.

As shown in FIG. 4, a plurality of seal protrusions 52 are formed on the outer peripheral surface of fuel pipe 50. Fuel pipe 50 and seal protrusions 52 are formed integrally from an elastic resin material. Seal protrusions 52 surround the outer peripheral surface of fuel pipe 50.

The outer diameter of fuel pipe 50 in the site where seal protrusions 52 are provided (i.e., diameter of the distal end of seal protrusions 52) is slightly larger than the inner diameter of discharge port 26. The outer diameter of fuel pipe 50 in other sites is almost equal to or slightly less than the inner diameter of discharge port 26. If fuel pipe 50 is inserted into discharge port 26, seal protrusions 52 are elastically deformed. As a result, fuel pipe 50 is joined to discharge port 26 and the gap therebetween is sealed. Because a plurality of seal protrusions 52 are provided in fuel pipe 50, fuel pipe 50 and discharge port 26 are tightly joined (and sealed).

Furthermore, as shown in FIG. 1, the other end of fuel pipe 50 is connected to a fuel filter 52. Fuel filter 52 removes fine foreign matter from the fuel discharged from fuel pump 10. The fuel from which fuel filter 52 removed the foreign matter is discharged to the outside of the fuel tank.

The mutual arrangement of bearing retaining portion 22, brush retaining sections 24, and discharge port 26 will be described below.

As shown in FIG. 2, bearing 28 (i.e., bearing retaining portion 22) is disposed substantially in the center of motor cover 16. Two brushes 38 (i.e., brush retaining portions 24), along with discharge port 26, are disposed in positions eccentric with respect to bearing retaining portion 22. Two brush retaining portions 24 are disposed in opposing positions sandwiching bearing retaining portion 22. Discharge port 26 is disposed in a position shifted through 90 degrees in the circumferential direction from brush retaining portion 24.

Therefore, in the cross section perpendicular to the axial direction of fuel pump 10, bearing retaining portion 22, brush retaining portions 24, and discharge port 26 are arranged in positions in which they do not interfere with each other. Thus, as shown in FIG. 3, bearing retaining portion 22, brush retaining portions 24, and discharge port 26 can be disposed so as to overlap in the axial direction. As a result, parts of the wall that forms the bearing retaining portion 22 are shared with the wall that forms the brush retaining portions 24, parts of the wall that forms the bearing retaining portion 22 are shared with the wall that forms discharge port 26, and parts of the wall that forms brush retaining portions 24 are shared with the wall that forms discharge port 26. Therefore, the length of fuel pump 10 in the axial direction can be shortened and fuel pump 10 (motor cover 16) can be made more compact in the radial direction thereof.

Operation of the above-described fuel pump 10 will be briefly described. If current is supplied to brushes 38 from an external power source, an electric current flows from brush 38 to coil 36, via commutator 34. If the current flows in coil 36, the armature 31 rotates and the impeller also rotates. If the impeller rotates, fuel is sucked into pump casing 11. The pressure of the fuel that was sucked in rises as the impeller rotates, and the fuel is then discharged into housing 12. The fuel discharged into housing 12 flows inside housing 12 toward motor cover 16 and is discharged from discharge port 26 into fuel filter 51 via fuel pipe 50

In the fuel pump 10 of the present representative embodiment, discharge port 26 is provided in a position shifted from the center of bearing retaining portion 22, and discharge port 26 and bearing retaining portion 22 are disposed so as to overlap in the axial direction. As a result, the axial length of the fuel pump 10 can be reduced and the installation ability thereof on the fuel tank can be improved.

Further, discharge port 26 and brush retaining portions 24 are disposed in positions shifted in the circumferential direction, and brush retaining portions 24 can be disposed in a position close to the axial center (shaft 32) of fuel pump 10. As a result, the circumferential velocity of commutator 34 with respect to brushes 38 can be decreased and wear of brushes 38 can be reduced. Furthermore, because discharge port 26 and brush retaining portions 24 are not disposed side by side in the radial direction, the diameter of motor cover 16 (i.e., diameter of fuel pump 10) can be reduced.

Furthermore, discharge hole 25 formed in motor cover 16 has been linearly formed parallel to the axial direction of fuel pump 10. As a result, the fuel located in the housing 12 can flow toward discharge port 26 along a straight line. Therefore, passage resistance can be reduced and pump efficiency can be increased.

The preferred representative embodiment of the present teachings have been described above, the explanation was given using, as an example, the present teachings is not limited to this type of configuration. For example, the joint structure of the discharge port 26 and fuel pipe 50 can be implemented in a variety of modes. FIGS. 5, 6, and 7 illustrate other examples of the joint structure of the discharge port and fuel pipe.

In the joint structure shown in FIG. 5, a thin wall portion 54 a is formed in the distal end of a fuel pipe 50 a, and an O ring 56 a is installed in thin wall portion 54 a. In a state where the fuel pipe was inserted into a discharge port 26 a, thin wall portion 54 a of a fuel pipe 50 a extends reaching the inside of a discharge hole 25 a. As a result, O ring 56 a comes into contact with the bottom surface of the discharge port 26 a, sandwiched by a motor cover 16 a and fuel pipe 50 a and compressed in the axial direction. As a result, O ring 56 a seals the space between discharge port 26 a and fuel pipe 50 a. In this joint structure, the direction in which the fuel pressure acts and the direction of the pressure force acting from fuel pipe 50 a upon O ring 56 a are on the same straight line. Therefore, even when high-pressure fuel is discharged from the fuel pump, O ring 56 a can provide for effective sealing.

In the joint structure shown in FIG. 6, a groove 58 b is formed in the fuel pipe 50 b, and an O ring 56 b is disposed in groove 58 b. The outer diameter of O ring 56 b is larger than the diameter of the discharge port 26 b. As a result, if the fuel pipe 50 b is inserted into the discharge port 26 b, O ring 26 b is compressed and deformed in the radial direction by the wall surface of discharge port 26 b. A seal is thereby provided between discharge port 26 b and fuel pipe 50 b. In such joint structure, because O ring 56 b is disposed in groove 58 b, O ring 56 b is prevented from falling out of fuel pipe 50 b. Therefore, installation of fuel pipe 50 b on the fuel pump is facilitated.

The joint structure shown in FIG. 7 is obtained by improving the joint structure shown in FIG. 5. That is, a hook 17 c is formed on the surface of the motor cover 16 c, and a flange 51 c is formed in the fuel pipe 50 c. If the fuel pipe 50 c is inserted into the discharge port 26 c, hook 17 c and flange 51 c are engaged. As a result, fuel pipe 50 c can be prevented from being pulled out from the motor cover 16 c and the fuel pipe 50 c can be reliably fixed to the fuel pump.

Furthermore, in the above-described fuel pump, a return check valve may be installed inside the discharge port to prevent the return flow of the fuel from the fuel pipe into the fuel pump.

As shown in FIGS. 8 and 9, a seal surface 125 a is formed substantially in the center of the bottom surface of the discharge port 126 so as to link the fuel outlet of the discharge hole 125 to the discharge port 126. A guide 162 is provided in a position at a predetermined height above the seal surface 125.

As shown in FIGS. 10 and 11, the guide 162 comprises a guiding portion 162 c for guiding a return check valve 160, a fixing portion 162 a disposed coaxially with the guiding portion 162 c, and a joining portion 162 b for joining the guiding portion 162 c and the fixing portion 162 a. As shown in FIGS. 8 and 9, the outer peripheral surface of the fixing portion 162 is fixed to the inner surface of discharge port 126. The guide 162 is thereby positioned inside discharge port 126.

Return check valve 160 is guided by guide 162. Return check valve 60 comprises a shaft portion 160 b inserted through guiding portion 162 c of guide 162 and a sealing portion 160 a formed in the lower end portion of the shaft portion 160 b. In a state where return check valve 160 is moved to the lower end, the sealing portion 160 a abuts against seal surface 125 a of discharge port 126, thereby preventing the fuel from flowing back to the housing from the side of discharge port 126. On the other hand, if the fuel pressure inside the housing rises and return check valve 160 moves upward, while being guided by guide 162, the sealing portion 160 a of return check valve 160 separates from seal surface 125 a and the fuel is discharged from inside the housing into discharge port 126.

As is clear from FIG. 9, in a state where the fuel pipe was inserted into the discharge port 126, return check valve 160 is positioned below the distal end of the fuel pipe 150. As a result, the diameter of sealing portion 160 a of return check valve 160 is not restricted by the shape of fuel pipe 150 and can be made larger than a fuel channel 150 a formed inside the fuel pipe 150. Therefore, the diameter of sealing portion 160 a can be increased and the pressure receiving surface (i.e., surface receiving the fuel pressure) of return check valve 160 can be increased in comparison with the case where the return check valve is disposed inside the fuel pipe. As a result, pressure sensitivity of return check valve 160 can be increased and pressure loss caused by return pressure valve 160 can be reduced.

Comparison of FIG. 3 and FIG. 8 clearly shows that in the embodiment shown in FIG. 8, the depth of discharge port 126 is increased due to the installation of return check valve 160 in discharge port 126. However, because the pressure sensitivity of return check valve 160 is increased, return check valve 160 can be opened and closed without delay in response to the fuel pressure and the stroke of return check valve 160 can be decreased. As a result, the depth of discharge port 126 is prevented from being too large.

Furthermore, in the above-described embodiments, an example was considered in which the motor cover was formed integrally, but the motor cover may be also obtained by assembling a plurality of parts.

As shown in FIG. 12 or FIG. 13, the motor cover can be composed of a first cover 264 (368) on the lower side and a second cover 266 (370) on the upper side that is assembled with the cover 264 (368) on the motor side. If the motor cover is thus composed of two parts, the two parts can be molded from different materials according to the mechanical properties (e.g., mechanical strength) required for each part.

Finally, although the preferred representative embodiments have been described in detail, the present embodiments are for illustrative purpose only and not restrictive. It is to be understood that various changes and modifications may be made without departing from the spirit or scope of the appended claims. In addition, the additional features and aspects disclosed herein also may be utilized singularly or in combination with the above aspects and features. 

1. A fuel pump comprising: a housing, a motor disposed within the housing, the motor having a motor shaft, and a motor cover attached to one end of the housing, the motor cover comprising a bearing retaining portion and a discharge port, wherein the bearing retaining portion retains a bearing that rotatably supports one end of the motor shaft, and the bearing retaining portion is formed in a center of the inner surface of the motor cover, wherein the discharge port is formed concavely from the outer surface of the motor cover and is designed to insert a fuel pipe, and wherein the discharge port is disposed in a position shifted from the bearing retaining portion.
 2. A fuel pump as in claim 1, wherein the motor comprises a commutator and a brush that comes into contact with the commutator, wherein the motor cover further comprises a brush retaining portion for retaining the brush, and wherein the brush retaining portion and the discharge port are arranged side by side in the circumferential direction, and the bearing retaining portion, discharge port, and brush retaining portion are arranged so as to overlap in the axial direction.
 3. A fuel pump as in claim 2, wherein walls according to at least one combination of the wall for forming the bearing retaining portion and the wall for forming the discharge port, the wall for forming the discharge port and the wall for forming the brush retaining portion, or the wall for forming the bearing retaining portion and the wall for forming the brush retaining portion, are shared.
 4. A fuel pump as in claim 3, wherein the motor cover further comprises a discharge hole which is formed in the bottom surface of the discharge port, and further comprising: a return check valve disposed in the discharged port, the return check valve opening and closing the discharge hole, and wherein in a state where the fuel pipe is inserted into the discharge port, the return check valve is positioned on the outside of the fuel pipe.
 5. A fuel pump as in claim 4, further comprising a guide for guiding the return check valve, the guide being disposed in the discharge port. 